Arch Linux Security Advisory ASA-202105-10
=========================================
Severity: High
Date    : 2021-05-19
CVE-ID  : CVE-2021-28651 CVE-2021-28652 CVE-2021-28662
Package : squid
Type    : denial of service
Remote  : Yes
Link    : https://security.archlinux.org/AVG-1949

Summary
======
The package squid before version 4.15-1 is vulnerable to denial of
service.

Resolution
=========
Upgrade to 4.15-1.

# pacman -Syu "squid>=4.15-1"

The problems have been fixed upstream in version 4.15.

Workaround
=========
- CVE-2021-28651 can be mitigated by disabling URN processing by the
proxy, by adding these lines to squid.conf:

acl URN proto URN
http_access deny URN

- CVE-2021-28652 can be mitigated by either disabling Cache Manager
access entirely if not needed, by placing the following line in
squid.conf before lines containing "allow":

http_access deny manager

or by hardening Cache Manager access privileges, for example: require
authentication or other access controls in http_access beyond the
default IP address restriction.

- No known mitigations exist for CVE-2021-28662.

Description
==========
- CVE-2021-28651 (denial of service)

Due to a buffer management bug Squid before version 4.15 is vulnerable
to a denial of service attack against the server it is operating on.
This attack is limited to proxies which attempt to resolve a "urn:"
resource identifier. Support for this resolving is enabled by default
in all Squid.

- CVE-2021-28652 (denial of service)

Due to an incorrect parser validation bug Squid before version 4.15 is
vulnerable to a denial of Service attack against the Cache Manager API.

- CVE-2021-28662 (denial of service)

Due to an input validation bug Squid before version 4.15 is vulnerable
to a denial of service against all clients using the proxy.

Impact
=====
A remote attacker can cause denial of service through crafted requests.

References
=========
https://github.com/squid-cache/squid/security/advisories/GHSA-ch36-9jhx-phm4
https://github.com/squid-cache/squid/security/advisories/GHSA-m47m-9hvw-7447
https://github.com/squid-cache/squid/security/advisories/GHSA-jjq6-mh2h-g39h
https://security.archlinux.org/CVE-2021-28651
https://security.archlinux.org/CVE-2021-28652
https://security.archlinux.org/CVE-2021-28662